Ground reservoir for the storage of liquefied gases at a low temperature

ABSTRACT

929,609. Soil stabilisation. CONCH INTERNATIONAL METHANE Ltd. Feb. 12, 1962, No. 5325/62. Class 68 (1). [Also in Group XXVIII] Freezing of the water-bearing earth surrounding a plurality of shafts 2 intended for stoning liquefied gases (see Group XXVIII) is effected by filling the shafts with water or drilling mud, introducing double pipes, and passing refrigerant therethrough until a sufficient layer of frozen earth is obtained and finally passing steam through the double pipes to thaw any ice formed in the liquid with which the shafts are filled. In a modification the shafts are filled with refrigerant which is afterwards withdrawn. Each shaft is lined with concrete, aluminium or steel. Specification 894,762 is referred to.

` M. NACHSHEN Nov. 8, 1966 3,283,511 GROUND REsERvoIR FOR THE STORAGE 0F LIQUEFIED GASES AT A LOW TEMPERATURE 2 Sheets-Sheet l Filed Dec. 14, 1962 QW Q y ll Attorneys N0V 8, 1966 M. NACHSHEN 3,283,511

GROUND RESERVOIR FOR THE STORAGE OF LIQUEFIED GASES AT A LOW TEMPERATURE Filed Dec. 14, 1962 2 Sheets-Sheet 2 FIG. 3.

. FIG. 4C

FIG. 4B

Maurice Ncchshen ATTORNEY United States Patent() 3.283,511 GRUND RESERVOIR FOR THE STORAGE F LIQUEFIED GASES AT A LOW TEMPERATURE Maurice Nachshen, London, England, assignor to Couch International Methane Limited, Nassau, The Bahamas, a company of The Bahamas Filed Dec. 14, 1962, Ser. No. 246,295 Claims priority, application Great Britain, Feb. 12, 1962, 5,325/ 62 7 Claims. (Cl. 61-.5)

This invention relates to the storage of liquefied gas fat low temperature.

In this specication, the expression liquefied gas means liquid which boils at `atmospheric pressure at a temperature below the ambient temperature. Examples `of such liquefied gases 4are liquefied nitrogen, liquefied air, liquefied methane, liquefied natural gas, liquefied propane and liquefied oxygen.

The invention relates in particular to a ground reservoir for the storage of liquefied gases at low temperature.

It has already been proposed in the applicants patent application No. 23,439 t-o store liquefied gases in a ground reservoir which comprises a hole in the surface of the earth, the earth formation surrounding the hole containing a liquid which will solidify when the reservoir is precoo'led or charged with the liquefied gas to be stored, and a thermally insulated roof completely covering said hole.

The ground reservoir according to the invention differs from this earlier proposal in that it comprises a group of substantially vertical shafts in the surface of the earth in close proximity to each other, the earth formation surrounding said group of shafts and between the individual shafts containing a lliquid which will solidify at low temperatures and which will remain solid when the reservoir is charged with the liquefied gas to be stored, means for filling and discharging liquefied -gas from the shafts, means for venting gas from the shafts, 'and one or rnore thermally insulated roofs covering said shafts.

The 'advantage of the -ground reservoir according to the invention as compared with the earlier proposed ground reservoir is that the freezing of the walls can be simplified and that the roofing costs can be reduced. Another advantage is that the capacity of the reservoir can be extended easily. Furthermore, it is possible to store several different liquefied gases.

In a preferred embodiment of the invention, lall the liquid in the earth formation between the individual shafts is frozen when the reservoir is in use. The advantage of this is that the efficiency of thereservoir is improved as the temperature gradients in the earth are reduced.

The invention will now be explained with reference to the drawings in which:

FIGURE 1 shows a horizontal cross-section A-A of the reservoir according to the invention,

FIGURE 2 `shows a vertical cross-section B-B of the reservoir according to the invention,

FIGURE 3 shows in vertical section a single roof covering a plurality of shafts, and

FIGURES 4A-4D illustrate successive steps in the production of a shaft.

In an earth formation 1, -a large number of shafts 2 are excavated. The shafts 2 are deep in relation to their width. Normally, the shafts 2 are circular in cross-section. The depth of each shaft 2 is, for example, 100 feet, and its diameter is, for example, feet. The shafts 2 are arranged in close proximity to each other. The earth formation 3 surrounding the group of shafts 2 and between -the individual shafts 2 contains a liquid which is in solid condition. Normally this liquid is water.

Each shaft 2 is provided at its top with a roof 4 made of aluminium, concrete, stainless steel, wood or another Mice suitable material. In order to prevent the influx of ambient heat, it is desirable to provide the roofs 4 with a layer of heat insulating material'. Instead of 1a curved roof 4, use can be made of a fiat roof 4.

Preferably, each shaft 2 is provided with a roof 4 of its own. It is however, also possible to make use of one roof covering more than one shaft 2, but it is advantageous to provide each shaft 2 with a roof of its own, since Ia roof covering one :shaft only spans a relatively small opening so that the roof can be made of a relatively light and simple construction. v

In use, it is possible to fill and `discharge liquid from each shaft 2 separately. It is, however, possible to interconnect the shafts 2 by Ian opening 5 at the bottom of the shaft 2 and by an opening 6 at the top of shaft 2. This has the advantage that only one loading and unloading tube and only one venting arrangement is necessary for a group of shafts 2. The group of shafts 2 can be divided in at least two subgroups, each shaft 2 of each subgroup being connected at the top 'and at the bottom to another Ishaft 2 yof the same subgroup by means of openings 6 and S respectively. In this way, each subgroup of shafts 2 forms a separate unit, and it is possible to load and unload each unit separately. Also it is possible to store different liquefied gases in the separate units, for example liquefied natural gas in one unit, liquefied methane in another unit and liquefied propane in a third unit. It will be clear that more than three units can be made and that more than three different liquefied gases can be stored if desired. By way of example, openings 5 and 6 connecting two adjacent shafts 2 have been illustrated only in FIGURES 1 and 2. It will be clear that similar connections can be mlade between other shafts 2, if desired. The top parts of the walls of the shafts 2 can be made of concrete 7 in order to prevent caving in of the walls of the shafts 2 `and in order to obtain a firm support for the roo-fs 4 or 4. The top opening 6 can be located in the concrete 7. The opening 5, .located near the bottom of the shaft 2, i-s preferably lined by means of a suitable length of pipe 8 in order to prevent erosion.

Excavation of the shafts 2 could be accomplished by large diameter mechanical `auger boring, or by excavation by special grabs, before freezing the ground.

During boring operations, if the ground is not stable enough to remain unsupported, the sides of each shaft 2 may be temporarily supported for the whole or part of its depth by metal or other casings, or where appropriate the shaft 2 may be kept filled or partly filled with water 12 or with drilling mud or other high density fluid, as shown in FIGURE 4A. On completion of the boring, double pipes 13, 14 are inserted into the water as shown in FIGURES 4B and 4C, -in the drilling mud or in the high density fluid in the shafts 2. The double pipes are lowered into the water, into the drilling mud or into the high density fluid near the walls of each shaft 2. Then a cold fiuid is circulated through the pipes, existing at outlet 16, and this circulation is continued until there is sufficient build-up of frozen earth around the periphery of each shaft 2. Sometimes it is not necessary to support the walls of shaft 2 during the boring operati-on. This is, for example, the case when the shafts are bored in clay, gravel, sandstone, chalk, or very dense sand.

In creating the required thickness 15 of frozen earth, part of the water or drilling mud will also freeze. Therefore it may sometimes be necessary to pass a hot fluid such as hot water or steam through the pipes in order to thaw the ice which is -i-n contact with the pipes. In this way, the part of the water or of the ydrilling mud which has been frozen can be melted again. The w-ater or drilling mud can then be removed from the shafts 2.

According to a modified method, lafter excavation of the shafts 2, the drilling mud is displaced by a liquid having a low freezing point but with sufficient density to support the sides of the shafts 2 before the freezing. When the drilling mud in the shafts 2 has been completely replaced by the low freezing liquid, this liquid could be reduced in temperature by any suitable means, for example by circulating -a cold fluid through pipes inserted into the -low freezing liquid, so that the ground around the periphery of (the .shafts will freeze. Instead the llow freezing liquid can be precooled before it is introduced into the shafts 2, so that upon introduction of it into the shafts 2 the ground around the shafts 2 will freeze almost immediately. After freezing of the ground, the low temperature liquid can be pumped out of the shafts.

When injecting the .flow freezing liquid into lthe shaft 2, a fiuid separating diaphragm can be used in order to prevent intermixing of the drilling mud and of the low freezing liquid.

In suitable strata a high density low freezing liquid may be used with-out the preliminary use of drilling mud. The llow-freezing liquid should Ibe immscible with the liquid ycontained in the earth.

When the walls of the shafts have been frozen and the drilling mud .or the low freezing liquid has been removed from the shafts, the roofs can be mounted, for example, as shown at 17 in Figure 4D, and then the ground reservoir is ready for receiving the liquefied gas -to Ibe stored.

If desired, the wal-ls of the shafts can be lined with a suitable material such as concrete, aluminium, stainless steel, steel, etc., although in most cases such a lining will not be necessary.

I claim:

1. A gro-und reservoir for the storage of liquefied gases at low temperature which comprises a group of substantially vertical shafts extending from the surface of the earth through the earth formation in close proximity to each other, a frozen liquid contained in the earth formation surrounding said group of shafts and between the individual shafts, said liquid solidifying at low temperatures and remaining solid when the reservoir is charged with the liquefied gas to be stored, said shafts being sufficiently close to each other so Ithat the solidified liquid completely occupies the space between adjacent shafts, means for filling and discharging liquid from the shafts, means for venting gas from the shafts, and at least one thermally insulated roof covering said shafts.

2. A reservoir as claimed in claim 1 in which each shaft is covered by an individual thermally insulated roof.

3. A reservoir as claimed in claim 1 in which one thermally insulated roof covers a plurality of shafts.

4. A reservoir yas claimed in claim 1 in which shafts of the group a-re interconnected at the top and at the bottom.

5. A ground reservoir for the storage of liquefied gases at low temperature which comprises a group of substantially vertical shafts extending from the surface of the earth through the earth formation of the ground in close proximity to each other, a frozen liquid contained in the earth formation surrounding said group of shafts and be- ,tween the individual shafts, said liquid solidifying at low temperatures and remaining solid when the reservoir is charged with the liquefied gas to be stored, said shafts being sufficiently close to each other so that the solidified liquid completely occupies the space between adjacent shafts, means for filling and discharging liquid from the shafts, means for venting gas from the shafts, at least one thermally insulated roof covering said shafts, the upper wall and rim of each shaft comprising a strong, rigid fabricated unit extending downwardly into Contact with the earth around each shaft, said units of adjacent shafts being rigidly joined together to form a unitary rigid top portion for a plurality of adjacent shafts.

6. A reservoir as claimed in claim 5, said fabricated units being made of concrete.

7. A method of constructing a ground reservoir for the storage of liquefied gases at low temperature, which comprises boring a plurality of shafts in close proximity to each other in moisture-containing earth, supporting the walls of the shafts by means of a high density fluid, lowering pipes into the high density iiuid near the walls of the shafts, freezing the earth walls of the shafts by circulating a cold fluid through the pipes to solidify all the earth moisture between the adjacent shafts, replacing the cold Ifluid inthe pipes by a warm fuid, circulating the warm fluid through the pipes so that the high density fluid which is frozen melts, removing the pipes and the high density fiuid from the shafts, and covering the shafts by at least one thermally insulated roof.

References Cited by the Examiner UNITED STATES PATENTS 363,419 5/1887 Poetsch 61-36.1 1,342,780 6/1920 Vedder 61-36.1 2,033,560 3/1936y Wells 61-36.1 2,193,219 3/1940 Bowie et al. 61-36.1 2,437,909 3/ 1948 Cooper 61-.5 2,661,062 12/1953 Edholm 61-.5 2,788,637 4/ 1957 Benz 61-.5 2,796,739 6/1957 Meade 61-36.1 2,803,114 8/1957 Hudson 61-.5 2,932,170 4/ 1960 Patterson et al. 6l-.5

CHARLES E. OCONNELL, Primary Examiner.

EARL I. WIT MER, Examiner.

R. A. STENZEL, Assistant Examiner. 

1. A GROUND RESERVOIR FOR THE STORAGE OF LIQUEFIED GASES AT LOW TEMPERATURE WHICH COMPRISES A GROUP OF SUBSTANTIALLY VERTICAL SHAFTS EXTENDING FROM THE SURFACE OF THE EARTH THROUGH THE EARTH FORMATION IN CLOSE PROXIMITY TO EACH OTHER, A FROZEN LIQUID CONTAINED IN THE EARTH FORMATION SURROUNDING SAID GROUP OF SHAFTS AND BETWEEN THE INDIVIDUAL SHAFTS, SAID LIQUID SOLIDIFYING AT LOW TEMPERATTURES AND REMAINING SOLID WHEN THE RESERVOIR IS CHANGED WITH THE LIQUEFIED GAS TO BE STORED, SAID SHAFTS BEING SUFFI- 